The letter, which cites various scientific studies, reads in part: "As the body that essentially sets industry standards, the NCC determines the quality of life for billions of birds. We urge you to update your guidelines with meaningful recommendations to address welfare concerns related to both growth rate and husbandry, reflecting the values and expectations of chicken consumers.

In response to the letter, Tom Super, National Chicken Council vice president of communications said: "We plan to respond to the letter ASPCA sent this morning to the National Chicken Council.

"Consumers want to be sure that all animals being raised for food are treated with respect and are properly cared for during their lives. The people and companies involved in raising chickens for food share the public’s concern.

"The ASPCA’s description of poultry production in the United States is not based on fact and in no way represents the realities of modern poultry production or the health and welfare of today’s chickens. The US national broiler flock is incredibly healthy and is the envy of the world. Mortality and condemnation rates for broilers, the most sensitive indicators of the health and well-being of any flock, are at historical lows.

"In fact, if we reverted to the way we used to raise chickens several decades ago, the mortality rate for chickens would increase 490 per cent.

"Consumers can learn about modern chicken breeding and production and watch videos of how they are raised by visiting: http://www.realtruthaboutchicken.com/.

"Because of better nutrition, breeding, genetics, veterinary attention and technology, which include optimum growing conditions within climate-controlled barns, it takes less time for chickens to naturally reach market weight – all without the use of hormones or steroids. A common misconception, broiler chickens are never caged and free to roam within barns, interact, and eat and drink at will.

"From a pure business standpoint, it would make zero business and economic sense for a farmer to do anything to a bird that would harm it. The birds are their livelihoods and chicken producers want to do everything possible to keep them healthy.

"To assist chicken producers and processors in this effort, the National Chicken Council developed the NCC Animal Welfare Guidelines and Audit Checklist which have been widely adopted within the industry. Periodically revised, this year’s updates will cover every phase of a chicken’s life and will offer the most up-to-date, science-based recommendations for the proper treatment and humane care of broiler chickens."

You can view the ASPCA's letter to the National Chicken Council by clicking here.